<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>注意点</title>
    <style>
        /* 浮动的盒子只影响浮动盒子后面的标准流，不会影响前面的标准流 */
        .front {
            width: 900px;
            height: 600px;
            background-color: pink;
        }

        .nav1 {
            width: 200px;
            height: 150px;
            background-color: gray;
        }

        .nav2 {
            width: 230px;
            height: 100px;
            background-color: purple;
            float: left;
        }

        .nav3 {
            width: 300px;
            height: 200px;
            background-color: orange;
        }

        .back {
            width: 900px;
            height: 600px;
            background-color: pink;
            margin: 20px 0 0 0;
        }

        .one1 {
            width: 200px;
            background-color: gray;
            float: left;
            height: 150px;
        }

        .one2 {
            width: 230px;
            height: 100px;
            background-color: purple;

        }

        /* one3 这个浮动去贴 one1 标准流的底部 */
        .one3 {
            width: 300px;
            height: 200px;
            background-color: orange;
        }
    </style>
</head>

<body>
    <div class="front">
        <div class="nav1">标准流</div>
        <div class="nav2">浮动</div>
        <div class="nav3">浮动</div>
    </div>
    <div class="back">
        <div class="one1">浮动</div>
        <div class="one2">标准流</div>
        <div class="one3">浮动</div>
    </div>
</body>

</html>